Preparation of Lithium Carbonate From Lithium Chloride Containing Brines

ABSTRACT

This invention relates to a method for the preparation of lithium carbonate from lithium chloride containing brines. The method can include a silica removal step, capturing lithium chloride, recovering lithium chloride, supplying lithium chloride to an electrochemical cell and producing lithium hydroxide, contacting the lithium hydroxide with carbon dioxide to produce lithium carbonate.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/172,540, filed on Apr. 24, 2009, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention generally relates to the field of recovering lithium fromlithium containing solutions. More particularly, the invention relatesto the preparation of lithium carbonate from lithium chloride containingbrines.

2. Description of the Prior Art

It is known that geothermal brines can include various metal ions,particularly alkali and alkaline earth metals, in varyingconcentrations, depending upon the source of the brine. Recovery ofthese metals is important to the chemical and pharmaceutical industries.

Geothermal brines are of particular interest for a variety of reasons.First, geothermal brines provide a source of power due to the fact thathot geothermal pools are stored at high pressure underground, which whenreleased to atmospheric pressure, can provide a flash-steam. Theflash-stream can be used, for example, to run a power plant.Additionally, geothermal brines typically contain various useful metals,such as, lithium, lead, silver and zinc, each of which can be recoveredfrom the brine for further use.

Lithium may be recovered from ores, as the ore may be baked withsulfuric acid, and the product leached with water. The resulting lithiumsulfate solution is treated with lime and soda ash to remove calcium andmagnesium, and lithium is then precipitated as a carbonate. Other knownmethods for recovering lithium from ores include alkaline methods andion-exchange methods, each of which can yield solutions of lithium ashydroxide, chloride or sulfate. These methods may also include theremoval of calcium and magnesium by treatment with lime and soda ash.

Typically, the economic recovery of lithium from natural, predominantlychloride, brines (which may vary widely in composition), depends notonly on the overall lithium content, but also upon the concentrations ofinterfering ions, particularly calcium and magnesium, which can greatlyeffect the performance and economics of the lithium recovery. Magnesiumcan be difficult to remove because it is chemically similar to lithiumin solution. Generally, at low concentrations, magnesium may be removedby precipitation with lime as magnesium carbonate. At higher magnesiumconcentrations, removal with lime is not feasible and various ionexchange and liquid-liquid extraction methods have been proposed.

Although conventional processing of ores and brines makes it possible toeliminate major portions of interfering ions, there remains a need forthe simplified removal of interfering ions from brines for theproduction of lithium carbonate.

SUMMARY OF THE INVENTION

A method for the preparation of lithium carbonate from a lithiumchloride containing solution is provided. Specifically, a method for thepreparation of lithium carbonate from geothermal, smackover, and otherbrines is provided.

In one aspect, a method for preparing lithium carbonate from a lithiumchloride containing solution is provided. The method includes the stepsof supplying a lithium chloride containing solution to a silica removalstep to produce a silica-lean lithium chloride containing solution,wherein the silica removal step is operable to remove at least a portionof silica present in the lithium chloride containing stream. Thesilica-lean lithium chloride containing solution is supplied to alithium chloride capture step, wherein the lithium chloride capture stepis operable to selectively capture said lithium chloride from thesilica-lean lithium chloride containing stream. Lithium chloride isrecovered from the lithium capture step to produce a lithium chloriderich stream. The lithium chloride-rich stream is supplied to anelectrochemical cell, wherein the electrochemical cell is maintained atconditions sufficient to produce a lithium hydroxide-rich solution. Thelithium hydroxide-rich solution is contacted with carbon dioxide toproduce lithium carbonate.

In certain embodiments, the method can further include a purificationstep for decreasing the concentration of at least one of calcium,magnesium, manganese or zinc ions present in the lithium chloride richstream after the lithium chloride recovery step. The purification stepcan include the steps of contacting the lithium chloride rich streamwith a base; adding a carbonate such that at least a portion of calcium,magnesium, manganese or zinc present precipitates as a solid; andseparating the precipitate from the lithium chloride rich stream toproduce a solid waste precipitate and a purified lithium chloride richstream, said purified lithium chloride rich stream having a lowerconcentration of at least one of calcium, magnesium, manganese or zinc.

In another aspect, a method for the preparation of lithium carbonatefrom a lithium chloride containing brine solution is provided. Themethod includes the steps of providing a lithium chloride containingbrine solution. At least a portion of silica present in said lithiumchloride containing solution is removed to produce a silica-lean lithiumchloride containing solution. Lithium chloride is isolated from saidsilica-lean lithium chloride containing solution. Isolated lithiumchloride is recovered to produce a lithium chloride-rich solution. Thelithium chloride-rich solution is supplied to an electrochemical cell,which is operated at conditions sufficient to produce a lithiumhydroxide solution. Lithium hydroxide solution from said electrochemicalcell. Lithium hydroxide solution is then contacted with carbon dioxideto produce a slurry that can include lithium carbonate. Lithiumcarbonate is then recovered from the slurry.

In another embodiment, a method for preparing lithium carbonate from alithium chloride containing brine solution is provided. The method caninclude the steps of supplying a substantially silica-free lithiumchloride solution to a lithium chloride capture step, wherein thelithium chloride capture step is operable to capture a substantialportion of the lithium chloride present in the silica-lean lithiumchloride containing stream; recovering lithium chloride from the lithiumcapture step to produce a concentrated lithium chloride rich stream;contacting the concentrated lithium chloride-rich stream and a sodiumcarbonate solution in a reaction vessel, wherein said sodium carbonatesolution is prepared by contacting a sodium hydroxide solution withcarbon dioxide gas, wherein the sodium hydroxide is prepared byelectrolyzing sodium chloride; separating a product stream from thereaction vessel to provide a lithium carbonate product and a streamcomprising sodium chloride; and optionally recycling at least a portionof the sodium chloride stream to the electrochemical cell for theproduction of sodium hydroxide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of the steps of a method for the production oflithium hydroxide from a geothermal brine according to one embodiment ofthe invention.

FIG. 2 is a flow chart of the steps of a method for the production oflithium carbonate from a geothermal brine according to one embodiment ofthe invention.

FIG. 3 is a schematic diagram of one embodiment of an apparatus for theproduction of lithium carbonate from a geothermal brine according to oneembodiment of the invention.

FIG. 4 is a schematic diagram of one embodiment of an apparatus for theproduction of lithium carbonate from a geothermal brine according to oneembodiment of the invention.

FIG. 5 is a schematic diagram of one embodiment of an apparatus for theproduction of lithium carbonate from a geothermal brine according to oneembodiment of the invention.

FIG. 6 shows the compares of lithium hydroxide concentration formultiple embodiments of the present invention.

FIG. 7 shows variation of cell voltage of an electrolysis cell duringpreparation of lithium hydroxide in one embodiment of the presentinvention.

FIG. 8 shows lithium hydroxide concentration as a function of currentefficiency in one embodiment of the present invention.

FIG. 9 shows energy consumption for production of lithium hydroxide inone embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Broadly, described herein are methods for the production of lithiumhydroxide and lithium carbonate from a lithium chloride containingsolution.

As shown in FIG. 1, in one embodiment, the method generally includes astep of providing a lithium chloride containing solution, such as forexample, a geothermal brine, a silica removal step, a lithium chlorideextraction step, an optional lithium chloride concentration step, anelectrochemical lithium hydroxide production step, an evaporation step,and a lithium hydroxide isolation and drying step.

As shown in FIG. 2, in one embodiment, the method generally includes astep of providing a lithium chloride containing solution, such as forexample, a geothermal brine, a silica removal step, a lithium chlorideextraction step, an optional lithium chloride concentration step, anelectrochemical lithium hydroxide production step, and a carbonationstep, whereby lithium hydroxide is converted to lithium carbonate.

As used herein, brine solution refers to a solution of alkali and/oralkaline earth metal salt(s) in water, wherein the concentration ofsalts can vary from trace amounts up to the point of saturation.Generally, brines suitable for the methods described herein can beaqueous solutions that may include alkali metal or alkaline earthchlorides, bromides, sulfates, hydroxides, nitrates, and the like, aswell as natural brines. Brines can be obtained from natural sources,such as, Chilean brines or Salton Sea geothermal resource brines,geothermal brines, sea water, mineral brines (e.g., lithium chloride orpotassium chloride brines), alkali metal salt brines, and industrialbrines, for example, industrial brines recovered from ore leaching,mineral dressing, and the like. The present methods are equallyapplicable to artificially prepared lithium chloride solutions.

Accordingly, the present methods include the preparation and recovery oflithium carbonate from solutions that include monovalent cations,including lithium, multivalent cations, monovalent anions, andmultivalent anions.

In certain embodiments, silica may be present in the lithium chloridecontaining solution or geothermal brine, and may be removed by a varietyof known methods (e.g., U.S. Pat. No. 4,016,075), prior to use in themethods described herein. Thus, in certain embodiments, the methods forthe preparation of lithium carbonate described herein can include asilica management step.

Referring to FIG. 1, provided herein is a multistep method for theisolation of lithium ions from a brine or other lithium containingsolution and the subsequent production of lithium carbonate therefrom.In a first step of the method, the brine is supplied to a silicamanagement step, wherein silica is removed from the brine to produce asilica-free brine or lithium containing solution. In a second step ofthe method, lithium ions are removed from the silica-free brine orlithium containing solution. Optionally, in a third step, the lithiumion containing solution from the second step may be concentrated toproduce a concentrated lithium ion containing solution. In a fourthstep, the lithium containing solution is supplied to an electrochemicalcell to produce a lithium hydroxide containing solution. In a fifthstep, water can removed from the lithium hydroxide containing solutionfrom step 4 to crystallize at least a portion of the lithium hydroxidefrom step 4. In a sixth step, the lithium hydroxide is isolated,recovered, and dried.

Referring to FIG. 2, provided is a multistep method for the isolation oflithium ions from a brine or other lithium containing solution and thesubsequent production of lithium carbonate therefrom. In a first step ofthe method, a brine is supplied to a silica management step, whereinsilica is removed from the brine to produce a silica-free brine orlithium containing solution. In a second step, lithium ions are removedfrom the silica-free brine or lithium containing solution. In anoptional third step, the lithium ion containing solution can beconcentrated to produce a concentrated lithium ion containing solution.In a fourth step, the lithium containing solution is supplied to anelectrochemical cell to produce lithium hydroxide. The lithium hydroxidecan be supplied to a fifth step where lithium hydroxide is converted tolithium carbonate. In a sixth step, lithium carbonate is isolated andrecovered.

Referring to FIG. 3, in one embodiment of the present method, lithiumchloride containing solution 10 is provided. As noted above, lithiumchloride containing solution 10 can be obtained from a variety ofsources, including geothermal brines. The lithium chloride containingsolution is supplied to silica management step 12, which operates tosignificantly reduce the amount of silica that may be present in lithiumchloride containing solution 10, such that silicate precipitate 16 andsilica-lean lithium chloride containing solution 14 are produced.Preferably, after the silica management step, the silicon concentrationin silica-lean lithium chloride containing solution 14 is less thanabout 150 ppm, more preferably the concentration is less than about 100ppm, even more preferably the concentration is less than about 50 ppm,and even more preferably the concentration is less than about 25 ppm. Incertain embodiments, the concentration of silicon in silica-lean lithiumchloride containing solution 14 is less than about 20 ppm, less thanabout 10 ppm, or even less than about 5 ppm. It is understood that thesilica management step may be omitted from the process for brines thatdo not include silica, or brines that have a substantially low initialsilica concentration.

In certain embodiments, silica management step 12 can include the stepof contacting lithium chloride containing solution 10 with activatedalumina to remove at least a portion of the silica present. Alumina thatincludes silica bound thereto can be regenerated by contacting thealumina with sodium hydroxide. Alternatively, the lithium chloridecontaining solution can be contacted with aluminum chloride, which isconverted to aluminum hydroxide, and can be used to precipitate silicapresent in the lithium chloride containing stream. In a furtherembodiment, iron (II) that may be present in certain lithium containingbrines can be oxidized with an oxidant, such as air, hypochlorite,hydrogen peroxide, oxygen, ozone, or a like oxidizing agent, to generateiron (III) chloride, which after adjustment of the pH to above about 5,from an initial pH of about 2.5 to 3.5, will precipitate ferrichydroxide. The ferric hydroxide can adsorb silica from the lithiumcontaining brine. In a preferred embodiment, the pH is adjusted tobetween about 5 and 6 to induce precipitation of silica and iron. Inalternate embodiments, the pH is adjusted to above at least about 4.5 toinduce precipitation of silica and iron. In certain embodiments, it ispreferred the pH is not increased above about 6, to prevent theprecipitation of other ionic species present in the lithium containingbrine. In yet another embodiment, iron (II) can be added to the lithiumchloride containing solution and oxidized by known means to iron (III),such as with by contacting the iron (II) with an oxidant, such as air,oxygen, ozone, hypochlorite, hydrogen peroxide, or other suitableoxidizing agent. Contacting silica present in the lithium chloridecontaining solution with the iron (III) compound forms a precipitatewhen the pH is adjusted to between about 4.5 and 6 with the addition oflime or similar base. It a preferred embodiment, the pH is adjusted tobetween about between about 5 and 6. In alternate embodiments, the pHmust be adjusted to above at least about 4.5 for the silica and iron toprecipitate. In certain embodiments, it is preferred the pH is notincreased above about 6, to prevent the precipitation of other ionicspecies.

In addition, silica management step 12 can include any known means forremoving a portion of the silica present in the feed stream, while atthe same time maintaining the initial concentration of lithium. In oneembodiment, lithium chloride containing solution 10 can be contactedwith aluminum chloride, iron chloride, aluminum hydroxide, or the like,to form a precipitate with the silicon dioxide. Contacting can befacilitated by known means, such as a mixing device. Solid silicaprecipitate 16 removed from lithium chloride containing solution 10 canbe collected and removed from the mixing or like device, by known means,such as screening or filtering, to yield lithium chloride containingstream 14 that is substantially free of silica.

As known in the art, various membranes can be used to selectively removespecific undesired ions from lithium containing solution 14.

Silica-lean lithium chloride containing stream 14, which issubstantially free of silica (measured as SiO₂), can be supplied tolithium chloride isolation step. In certain embodiments, silica-leanlithium chloride containing stream 14 can be supplied to at least oneintercalated lithium absorbent column 18, which can be configured toabsorb and isolate lithium chloride from the silica-lean lithiumchloride containing solution, while at the same time allowing otherions, such as calcium, magnesium, and/or sodium, or the like, to passwith water stream 22, through the use of a selective molecular sieve,membrane, or other like materials. In embodiments that include more thanone intercalated lithium absorbent column, the bulk of the lithium canbe removed in the first intercalated lithium absorbent column, with anysubsequent “polishing” intercalated lithium absorbent columns being usedto minimize overall lithium loss during the recovery process.

In certain embodiments, the intercalated lithium absorbent column can beoperated as follows. Lithium alumina intercalate particles having anaverage diameter of between about 100 and 150 μm can be combined with asaturated sodium chloride solution that includes approximately 200 ppmlithium chloride to prepare a slurry, which can then be added to thecolumn. The column may be jacketed, insulated or may include means toprovide heating or cooling to the column. The column may include amethod of distributing liquid and support for the extraction media andcan include fitted ends having a pore size of between approximately 25and 50 μm, although other like means, such as supports of glass wool orperforated plates, can also be used instead of fitted ends. For thepresent invention, the operating temperature of the column can bemaintained at a temperature that is greater than room temperature, andis preferably maintained at a temperature above about 70° C., morepreferably between about 95° C. and 110° C.

The column is maintained wet and is unloaded before the first use bycirculating at least about 1 bed volume, preferably about two bedvolumes, of deionized water 20 that includes approximately 1000 ppmlithium chloride, at a flow rate of between approximately 1 and 4 bedvolumes/hour, preferably between about 1.5 and 2.5 bed volumes/hour. Thecolumn is then contacted with approximately one bed volumes of saturatedsodium chloride solution containing approximately 200 ppm lithiumchloride is then run.

During loading of the column (i.e., during the step of capturing desiredlithium chloride), high ionic strength solution 14 containing lithiumchloride is supplied to column 18 and the lithium concentration of theeffluent at column outlet 22 is measured to determine the point at whichthe column becomes saturated with the lithium chloride. During thelithium ion capture step, the lithium concentration at outlet 22 remainsfairly constant and relatively low, for example, approximately 0 and 100ppm. The point at which column 18 reaches or nears the point ofsaturation with lithium ions, however, the concentration of the lithiumin the effluent increases, thus indicating that the column has eitherlittle or no capacity for additional lithium ions. Upon reaching thispoint of saturation, flow of the solution that includes lithium chlorideto column 18 stopped, and the column is flushed with between about 1 and8 bed volumes of deionized water, preferably between about 1 and 2.5 bedvolumes, and most preferably between about 1 and 1.5 bed volumes, toproduce a lithium chloride-rich stream 24. It is understood that theapparatus can include various valves and control devices for controllingthe flow of the lithium containing solution or the wash solution to thecolumn.

In certain embodiments, after loading of the column, but beforecollection of the captured lithium chloride, the column may be flushedwith about 1 bed volume of a 26% saturated sodium chloride solution thatincludes about 200 ppm lithium chloride.

After the removal of lithium chloride from the lithium containing feedstream during the lithium chloride isolation step, intercalated lithiumabsorbent columns 18 can be regenerated and the lithium chloriderecovered therefrom. Specifically, at least about 0.5 equivalents ofwash water 20 may be supplied to column(s) 18 to remove absorbed lithiumchloride and produce lithium chloride rich solution 24. In certainembodiments, between about 1 to 2 equivalents of wash water 20, or moreequivalents, may be used during the regeneration of the columns. Inpreferred embodiments, the wash water may include lithium ions for theregeneration of the columns. Optionally, low ionic strength liquids,such as alcohols and water/alcohol mixtures can be used to regeneratethe columns. In general, the amount of water utilized from the lithiumchloride recovery from the column is minimized by recycling the productstreams to maximize lithium content, without affecting the capacity ofthe extracting media.

Optionally, a purification step can be employed to remove calcium,magnesium, or other divalent ions such as zinc and manganese that may bepresent in lithium chloride-rich stream 24. Removal of calcium,magnesium, and/or other alkaline earth metals can be achieved by knownmeans, such as, by increasing the pH and treating the solution with ionexchange, preferably using selective chelating ion exchange resins, orby the addition of a base, such as lime, sodium hydroxide, lithiumhydroxide, or the like, followed by the addition of lithium carbonate,sodium carbonate, potassium carbonate, ammonium carbonate, or othersuitable carbonate, which can precipitate magnesium and iron hydroxide,as well as calcium carbonate. In alternate embodiments, ion exchangemeans can be employed to facilitate the removal of calcium, magnesium,and/or other alkaline earth metals. Other bases, such as sodiumhydroxide and other hydroxides of alkali metals, can also be used. Incertain brines, it may be beneficial to remove boron from the productstream at this point process by known means, such as by precipitation,solvent extraction, or ion exchange.

Lithium chloride-rich stream 24 may have a concentration of betweenabout 1% and 42% by weight, preferably greater than about 10% by weight,more preferably greater than about 25% by weight. In alternateembodiments, lithium chloride-rich stream 24 may have a concentration ofgreater than about 10% by weight.

In certain embodiments, lithium chloride containing solution 24 canoptionally undergo a purification or concentration step prior to beingprovided to electrolytic process 32. Methods for the isolation andpurification of lithium chloride from brines, including geothermalbrines, are known in the art, for example, as described in U.S. Pat.Nos. 4,036,713 and 5,951,843, each of which is herein incorporated byreference in its entirety.

Optionally, the process can include steps for increasing theconcentration of the lithium chloride stream. Specifically, lithiumconcentration means 26 can be utilized for the removal of a portion ofthe water in the lithium chloride stream, for example, by evaporation,thereby producing a more concentrated lithium chloride solution 30.Exemplary concentration means can include electrodialysis, steamevaporation, or solar evaporation. Water 28 removed from the lithiumchloride containing solution can be recovered, for example byevaporation and subsequent condensation, and resupplied to intercalatedlithium absorbent column(s) 18, or can be supplied to any other step inthis or an associated process that requires the supply of water.Alternatively, water 28 can be supplied to a geothermal well. Inembodiments employing a concentration step, overall concentration ofconcentrated lithium chloride-rich solution 30 can be increased togreater than 25% lithium chloride by weight, preferably up to about 40%lithium chloride by weight.

Concentrated lithium chloride-rich solution 30 can be supplied toelectrochemical cell 32, which includes at least one anode, one cathodeand a permeable membrane, for the electrochemical preparation of lithiumhydroxide. Electrochemical cells suitable for large scale production arecommercially available from companies, such as, DeNora, ChlorineEngineers, and Asahi Glass, to name a few. Specifically, chloride ionsare oxidized to chlorine at the anode and water is reduced to hydroxideions and hydrogen gas at the cathode. Preferably, concentrated lithiumchloride-rich solution 30 is substantially free of other ions,particularly ions that may interfere with the electrochemical reaction.Optionally, a lithium chloride-rich stream can supplied directly to theelectrochemical reaction, without being first being subjected to thesilica management and lithium ion sequestration steps, provided that thelithium chloride-rich stream is substantially free of non-lithium ions,particularly non-lithium ions that may interfere with theelectrochemical reaction. In certain embodiments, the concentration ofsodium and/or potassium ions in concentrated lithium chloride-richsolution 30 is less than about 5% by weight, preferably less than about3% by weight. Cations such as iron, calcium, magnesium, and the like, ifat all present, preferably have a total concentration of less than about0.001% by weight, more preferably less than about 0.005% by weight, andeven more preferably less than about 0.00001% by weight. Higherconcentrations of the interfering ions does not necessarily precludeoperation of the electrochemical cell, but instead may reduce theoverall life of the cell components and/or the overall effectiveness ofthe reaction.

Similar to that which is noted above with respect to the presence ofnon-lithium interfering cations, electrochemical cell 32 preferably hasa total non-chloride anion content of less than about 5% by weight,preferably less than about 3% by weight, and even more preferably lessthan about 1% by weight.

The cathode of electrochemical cell 32 can be any suitable material,including nickel, catalyzed nickel mesh, stainless steel, coatedstainless steel, mild steel, and the like. Other exemplary catalysts caninclude mixed ruthenium compounds, platinum and other similar compoundsthat have low hydrogen over potential. The total area of the cathode canbe adjusted based upon reactor size and desired production. Thecatholyte feed of the electrochemical cell 32 can be any suitablematerial having sufficient ions to carry a current. While water may beemployed, and in certain embodiments, the addition of lithium carbonateor lithium hydroxide may be beneficial to the operation of the cell.

The anode of electrochemical cell 32 can be any suitable material, suchas titanium mesh coated with ruthenium oxide, titanium mesh coated withplatinum, carbon, or the like. Preferably, the anode is a dimensionallystable anode, allowing for reduced power consumption. Dimensionallystable titanium anodes are particularly well-suited for chlorineenvironments as the titanium substrate is resistant to corrosion. Thetotal area of the anode can be adjusted based upon reactor size anddesired production. The anolyte of electrochemical cell 32 can be anysuitable material, including a lithium chloride solution having aconcentration of between of about 1% by weight to saturation, preferablybetween 5% and 40% by weight, more preferably between about 10% and 35%by weight.

The materials for construction of electrochemical cell 32 can be anymaterial that is chemically resistant to chlorine, activated chlorine,oxygenated chlorine species, and other dissolved species that may existin brine solutions. Exemplary materials for the construction ofelectrochemical cell 32 include polytetrafluoroethylene (PTFE),polyvinylidene fluoride (PVDF), HALAR (alternating co-polymers ofethylene and chlorotrifluoroethylene (CTFE)), and other fluorinated orpartially fluorinated.

The membrane of electrochemical cell 32 can be any suitablesemi-permeable cation selective membrane that selectively passes cationsand inhibits the passage of anions. Such membranes are known in the art.One exemplary membrane is Nafion (E.I. DuPont de Nemours & Co.),particularly the Nation 300, 400 and 900/9000 series of materials. Othersuitable membranes can be supplied by Flemion, however any suitablemembrane material can be used provided the material is chemicallyresistant to both chlorine and lithium hydroxide. The membrane may beplaced between the anolyte being electrolyzed and the catholyte.

In certain embodiments, the process can optionally include one or morefilter or separation-purification step prior to the step of supplyingconcentrated lithium chloride solution 30 or brine to electrochemicalcell 32.

During operation of electrochemical cell 32, a current density ofbetween about 500 and 10,000 A/m² can be applied at a voltage of betweenabout 1.5 and 5 volts. Preferably, a current density of between about2000 and 7000 A/m² is applied.

Electrochemical cell 32 may be operated at a temperature of betweenabout 60° and 100° C., preferably between about 70° and 95° C., and morepreferably between about 90° and 95° C. Cell 32 can be operated atatmospheric pressure, or slightly above atmospheric pressure.

Operation of electrochemical cell 32 produces lithium hydroxide insolution, and also evolves chlorine and hydrogen gas by products, whichcan be removed from the electrochemical cell via lines 34 and 35,respectively.

The efficiency of electrochemical cell 32 is at least about 60%,preferably at least about 70%, more preferably at least about 80%, morepreferably at least about 90%, more preferably at least about 95%, andeven more preferably at up to about 99.9%. The electrolysis can beoperated continually until the lithium hydroxide content reaches about17% by weight, at which time the lithium hydroxide solution may beremoved and supplied to a carbonation reactor. At lithium hydroxideconcentrations greater than about 17% by weight, the lithium hydroxidein solution can begin to precipitate. Electrochemical cell 32 can alsobe operated under conditions designed to produce lower concentrationlithium hydroxide solutions and the lower concentration lithiumhydroxide solution can be recycled to and from the carbonation reactor.In certain embodiments, electrochemical cell 32 can also include a feedline (not shown) for supplying water, low concentration lithiumhydroxide, low concentration lithium carbonate, or combinations thereofto the cell.

Lithium hydroxide solution 36 is supplied from electrochemical cell 32to carbonation reactor/absorber 38 and can be contacted with carbondioxide gas 44, for example, in an up-flow fashion. Carbonationreactor/absorber 38 can include a series of trays or other like meansthat are designed to allow lithium hydroxide 36 to be supplied to thetop of the reactor and flow in a downward fashion through the reactor,thereby contacting up-flowing carbon dioxide gas 44, which can beintroduced near the bottom of carbonation reactor/absorber 38. Inalternate embodiments, carbonation reactor/absorber 38 can includevarious mixing means designed to facilitate mixing of liquids and gases.Optionally, carbonation reactor/absorber 38 can be a jacketed batchreactor having thermostatic heating. The reaction produces lithiumcarbonate solid. The concentration of the lithium carbonate slurry ispreferably at least about 1.5% by weight lithium carbonate, morepreferably at least about 6% by weight lithium carbonate. Carbon dioxidecan be captured and recycled to carbonation reactor/absorber 38 via line42.

In certain embodiments, the lithium carbonate can produced by reactionof lithium hydroxide with sodium carbonate in water, wherein the mixtureis heated, preferably to a temperature of between about 90° C. and 95°C., with stirring. The reaction produces solid lithium carbonate and asodium chloride solution, wherein the sodium chloride solution can beseparated by filtration from the desired lithium carbonate solids.

Lithium carbonate solution 40 can be supplied to filtration means 46,which is operable to separate lithium carbonate containing slurry 40into water stream 52, which may optionally be resupplied to thefiltration means, and solid lithium carbonate product 50. Filtrationmeans 46 can, for example, include a series of screens or filters andwater supply 48. Optionally, water can be recycled to the process vialine 52. Optionally, lithium carbonate can be concentrated from theslurry by centrifugation or decantation thickening. Water collectedduring the separation of the solids from the slurry via filtration means46 can be supplied to the electrochemical cell, or may be supplied to ageothermal well or reservoir. In certain embodiments, lithium carbonatesolid can be retained on a band filter and supplied to a wash step,wherein hot water, preferably having a temperature of between about 90°C. and 95° C. is used to wash the solids. In certain embodiments, theaqueous solution collected via filtration means 46 can have a pH ofgreater than about 9, most likely having a pH between about 10-12.Alternatively, sufficient acid can be added to the aqueous solution toachieve a pH of between about 5 and 8.5, and the acidified water canthen be supplied to the intercalated lithium absorbent column(s).Alternatively, the solution can be returned directly to the cathode sideof the electrolysis cell without prior neutralization.

The solid lithium carbonate 50 is supplied to a drying station 54, whichcan optionally include heating means, as well as lines for supplyingnitrogen or other inert gases to the chamber. Dried lithium carbonateproduct 56 can then be collected, packaged and transported for furtheruse.

Referring now to FIG. 4, an alternate embodiment for the production oflithium carbonate is provided. Lithium chloride stream 30 is provided bythe process described above and as shown in FIG. 3. To electrochemicalcell 32, which is as described above, sodium chloride stream 60 isprovided. Sodium chloride stream 60 is then subjected to electrolysis toproduce sodium hydroxide stream 62 and chlorine and hydrogen gases 64.Reaction conditions for the production of sodium hydroxide byelectrolysis of sodium chloride are known in the art.

In certain embodiments, the efficiency of the electrolysis of sodiumchloride is at least about 70%, alternatively at least about 80%,alternatively at least about 90%, or alternatively at least about 95%.In certain embodiments, sodium hydroxide solution 62 is produced in at aconcentration of at least about 10% by weight, more preferably at leastabout 30% by weight, and most preferably about 35% by weight.

Chlorine and hydrogen gases 64, 65 from electrochemical cell 32 can becombusted and scrubbed with water to generate hydrochloric acid, whichmay be used within the process, or alternately may be purified,compressed, and sold commercially.

Sodium hydroxide stream 62 is supplied to carbonation reactor/absorber38, wherein the sodium hydroxide stream is contacted with carbon dioxidesteam 44, for example, in an up-flow fashion. Carbonationreactor/absorber 38 can include a series of trays, designed to allowsodium hydroxide stream 62 to be supplied to the top of the reactor andflow in a downward fashion through the reactor, thereby contacting upflowing carbon dioxide gas 44, which can be introduced near the bottomof the reactor, to produce sodium carbonate solution or slurry 66. Inalternate embodiments, carbonation reactor/absorber 38 can includevarious mixing means designed to facilitate mixing of liquids and gases.The concentration of the solution is preferably at least 15% by weightsodium carbonate, more preferably at least 25% by weight sodiumcarbonate. Carbon dioxide can be captured and recycled to carbonationreactor/absorber 38 via line 42.

Sodium carbonate solution 66 is supplied to reaction vessel 68 whereinthe solution is contacted with lithium chloride solution 30 to produceslurry 70, which includes lithium carbonate and sodium chloridesolution. The step of contacting sodium carbonate solution 66 andlithium chloride solution 30 in the reaction vessel can be at atemperature greater than about 60° C., preferably greater than about 80°C., and even more preferably between about 90° C. and 95° C. In certainembodiments, reaction vessel 68 can be a stirred tank reactor.Alternatively, reaction vessel 68 can be a standard crystallizer.Lithium carbonate is present as a precipitate, while sodium chlorideremains in aqueous solution.

Slurry 70, which includes solid lithium carbonate and aqueous sodiumchloride, is supplied to separator 72, which can include various meansfor the separation of solids from liquids including, for example,centrifuge, settling tank, filters, screens, and the like, to producelithium carbonate product stream 74 and sodium chloride brine solution76. In order to attain improved product quality, the lithium carbonatecan be treated to remove sodium, potassium, and/or chloride ions trappedin the interstitial space of the lithium carbonate precipitate, such asby washing with water, preferably hot water, or by like means. Incertain embodiments, separator means 72 can be a band filter or rotarydrum, and can optionally be fed through a counter current wash systemfor the removal of residual sodium chloride. Separator means 72 can alsoinclude water inlet 72 and outlet 76 for the washing of the separatedsolid lithium carbonate. Separator means 72 can also include means fordrying and/or the removal of water from the solid lithium carbonate,including for example, centrifuge, heaters, blowers, presses, and thelike. Separator means 72 can include a vacuum filter for removal ofwater. In certain embodiments, it is desirable to optimize the washingstep to both maximize purity of the lithium carbonate while minimizingthe amount of water used for washing. Sodium chloride solution 76 can berecycled to electrochemical cell 32 for electrolysis. Lithium carbonateproduct 74 can have a moisture content of less than about 5% by weight,preferably less than about 2% by weight, and even more preferably lessthan about 0.5% by weight.

The brine solution 76 from separator means 72 can include sodiumchloride and lithium carbonate. Generally, depending upon the amount ofwater utilized in the process and during the wash process, the ratio ofsodium chloride to lithium carbonate is at least about 20:1, morepreferably at least about 25:1, and even more preferably at least 30:1.In certain embodiments, the ratio of sodium chloride to lithiumcarbonate in the brine solution can be about 35:1.

In certain embodiments, brine solution 76 can be acidified withhydrochloric acid (not shown) to a pH of less than about 4, preferablyabout 3, and recycled to electrochemical cell 32. The hydrochloric acidcan be supplied from electrochemical cell 32.

The lithium carbonate production method proposed in FIG. 4 isadvantageous because the process eliminates, or nearly eliminates, theproduction of waste products. Specifically, in certain embodiments, therecycle of unused metal salts, for example sodium chloride, and carbondioxide, the overall yield can be quantitative or nearly quantitative.

Referring now to FIG. 5, another alternate embodiment for the productionof lithium carbonate is provided. The method is a single step processwherein sodium carbonate is produced and reacted with recovered lithiumchloride, however may require additional input and produces a wastelithium chloride stream that may include small amounts of lithiumcarbonate entrained therein.

A lithium chloride stream is provided as described above and as shown inFIG. 3. To electrochemical cell 32 sodium chloride stream 60 isprovided. Sodium chloride stream 60 is subjected to electrolysis toproduce sodium hydroxide 62 and chlorine and hydrogen gases 64, 65,respectively.

Sodium hydroxide stream 62 is supplied to mixer 80, wherein the sodiumhydroxide stream is combined and mixed with lithium chloride stream 30.Mixing of sodium hydroxide stream 62 and lithium chloride stream 30 canbe by known means, such as by agitators or mixers, with ultrasonicwaves, or by the like. Mixer 80 produces mixed stream 82, which includessodium hydroxide and lithium chloride in aqueous solution. In certainembodiments, it may be preferred that lithium chloride steam 30 has aconcentration of at least about 20% by weight, more preferably at leastabout 28% by weight, and even more preferably about 42% by weight.Similarly, in certain embodiments, it may be preferred that sodiumhydroxide stream 62 has a concentration of at least about 15% by weight,more preferably at least about 25% by weight, and even more preferablyabout 35% by weight.

Mixed stream 82 is supplied to carbonation reactor/absorber 84, whichcan include a series of trays, designed to allow the mixed stream, whichincludes lithium chloride and sodium hydroxide, to be supplied to thetop of the reactor and flow in a downward fashion through the reactor,thereby allowing the mixed stream to sufficiently contact up-flowingcarbon dioxide gas 44, which can be introduced near the bottom of thereactor via line 22, to produce a lithium carbonate slurry 90.Preferably, carbonation reactor/absorber 84 is maintained at atemperature of between about 90° C. and 100° C. In alternateembodiments, reactor 84 can include various mixing means designed tofacilitate mixing of liquids and gases. The concentration of the lithiumcarbonate is preferably at least 15% by weight, more preferably at least25% by weight lithium carbonate. Carbon dioxide can be recycled tocarbonation reactor 38 via line 42.

Lithium carbonate solution 90 is supplied to separation vessel 92wherein solid lithium carbonate is produced via line 94. A solution thatincludes sodium chloride and possibly a small amount of lithiumcarbonate is produced as stream 96.

Sodium carbonate solution 90, which includes solid lithium carbonate andaqueous sodium chloride, is supplied to separator means 92, which caninclude various means for the separation of solids from liquidsincluding, for example, centrifuge, settling tank, filters, screens, andthe like. Separator means 92 can also include water inlets and outlets(not shown) for the washing of the separated solid lithium carbonate.Separator means 72 can also include means for drying and/or the removalof water from the solid lithium carbonate, including for example,centrifuge, heaters, blowers, presses, and the like. A solid sodiumcarbonate product is collected via line 94. Optionally, a portion ofsodium chloride stream 96 can be recycled to electrochemical cell 32.Optionally, the sodium chloride solution can be recycled to the washingstep of the lithium extraction media. In certain embodiments, the sodiumchloride required for the process can be generated by the selectivecrystallization of sodium chloride from the geothermal, Smackover, orother brine.

In certain embodiments, the process may include means for theneutralization of any lithium carbonate that is included in the sodiumchloride solution, such as by neutralizing the solution by adding aneffective amount of hydrochloric acid or like acid. In embodimentswherein the lithium carbonate can be effectively removed, the solutioncan be recycled to the electrochemical cell, however, any lithiumcarbonate included therein may cause problems with the performance ofthe electrochemical cell.

EXAMPLES Example 1

Carbonation of Sodium Hydroxide. Carbonation of sodium hydroxide wascarried out using a 3 liter jacketed reactor with a heating system(manufactured by Syrris Reactor Systems, UK). The reaction was carriedout at a temperature of about 95° C. using a one liter of a 9.5 Msolution of sodium hydroxide (27.5% solids). Carbon dioxide was suppliedfor about 1 hour at the rate of 3 L/min. (totaling approximately 8moles, approximately 1.7 molar equivalents) to ensure the completeconversion of sodium hydroxide. At the end of the carbonation of thesodium hydroxide solution, a clear solution of sodium carbonate wasobtained, at which point the carbonation reaction was stopped andheating of the sodium carbonate solution was continued for few minutes.To the clear solution, lithium carbonate seeds were added beforereacting it with a lithium chloride solution (404 g lithium chloride in1000 mL). Experimental yield was 95%. Yields varied for other similarreactions depending upon experimental conditions and were as high asabout 100% in some cases. The purity of the isolated lithium carbonatewas approximately 96.6% before washing.

Before the first washing of the product stream, the lithium carbonatehad the following impurities: Na (71 mg/kg), Ca (2.8 mg/kg), Mg (2.1mg/kg), Fe (0.3 mg/kg), Ba (0.1 mg/kg), Mn (0.08 mg/kg), and Sr (0.03mg/kg), for a purity of about 78.4%. After washing with approximately2-3 volume equivalents of water, the sodium concentration is reduced toundetectable levels and the lithium carbonate had the followingimpurities: Mg (5.9 mg/kg), Ca (2.9 mg/kg), Ba (0.4 mg/kg), Fe (0.4mg/kg), Mn (0.07 mg/kg), and Sr (0.07 mg/kg), for a purity of greaterthan 99%.

The washing conditions may affect the amount of sodiumcarbonate/chloride entrained in the lithium carbonate product.

Example 2

The electrolysis process converts a purified, concentrated lithiumchloride solution into a concentrated lithium hydroxide solution forsubsequent conversion to lithium bicarbonate. The limiting factordetermining the efficiency of the electrochemical cell is theconcentration of lithium hydroxide in the catholyte, due toback-migration of hydroxide across the membrane. Therefore, theexperiment was designed wherein the electrochemical cell was operated atfour different hydroxide concentrations to map the effect of the lithiumhydroxide concentration and determine the maximum concentration thatcould be prepared. The experiment was designed to measure the currentefficiency and energy utilization of the dialysis process as a functionof hydroxide concentration. Within the electrochemical cell, under anapplied field, lithium cations migrate from the anolyte to catholyte,while water present is electrolyzed to H₂ and OH⁻ at the cathode. Intheory, each electron passed in the external circuit corresponds to anincrease of one lithium hydroxide molecule in the catholyte, leading toan increase in concentration of lithium hydroxide with time. The maininefficiency in the process, the back migration of OH⁻ ions fromcatholyte to anolyte, is dependent on the OH⁻ concentration of thecatholyte. Therefore, the experiments reported here were performed withthe intention of maintaining the OH⁻ concentration of the catholyteconstant by adding water at a known rate. The efficiency of the reactionwas measured by comparing the actual rate of addition of water with thetheoretical addition.

Example 3

Electrolytic Production of Lithium Hydroxide from Lithium Chloride.

Experimental Set-Up. The electrolysis system consisted of theelectrolysis cell having anolyte and catholyte flow systems.Electrolysis of lithium chloride solutions was carried out using an FM01electrolyzer (a scale model of the FM21 electrolyzer used commerciallyin the chlor-alkali industry) manufatured by ICI. The electrolyzerincluded lantern blade-style electrodes (anode: ruthenium oxide coatedtitanium; and cathode: nickel), and a Nafion® 982 membrane. The activesurface area of each electrode was about 64 cm² (4×16 cm), and the cellgap (distance measured anode to cathode) was between about 12-13 mm. TheFM01 electrolyzer was operated with the flow parallel to the 16 cmdirection (as compared with a flow direction parallel to the 4 cmdimension, as it is intended to be operated), as this improved themanagement of chlorine and hydrogen gasses evolved from the electrodes.In addition, although anolyte and catholyte flows are normally fed fromopposite sides of the cell, in the present experiment, the anolyte andcatholyte were fed from the same side of the electrochemical cell.

The anolyte flow system included a feed tank, pump, degassing tank,chlorine scrubber, and collection tank. A lithium chloride solutionhaving a concentration of about 21% by weight was placed in the anolytefeed tank and heated to about 90° C. The heated solution was pumped intothe anode chamber of the cell in a single pass mode at a flow rate ofabout 20 cm³/min, corresponding to a face velocity of about 0.13 cm/s.Upon exiting the cell, the lithium chloride solution and entrainedchlorine gas (produced at the anode) were passed through into adegassing tank, which was equipped with a chlorine scrubber, to removethe chlorine. The lithium chloride solution was then pumped into acollection tank for storage.

The catholyte flow system included a feed tank, pump, and water feedsystem. Lithium hydroxide was placed in the feed tank and heated toabout 95° C. and fed to the cathode chamber of the electrochemical cellin recirculating mode at a flow rate of about 50 mL/min, correspondingto a face velocity of about 0.33 cm/s. Water was added continuously tothe system using a peristaltic pump to maintain a constant lithiumhydroxide concentration. The rate of addition was monitored by theweight loss of the water tank. Nitrogen was bubbled through thecatholyte recirculation tank to minimize the reaction of lithiumhydroxide and carbon dioxide from the air.

Table 1 summarizes the experimental conditions used in tests todetermine the effect of the concentration of the catholyte.

TABLE 1 Experimental parameters for electrolysis experiments. ParameterValue Current Density 3000 A/m⁻² Electrode Area   64 cm² Anolyte Volume  60 cm³ Catholyte Volume   60 cm³ LiCl Inlet Concentration 21 wt % LiClInlet pH 0.5-0.7 Temperature 90° C. Time of Operation 2-3 hours Anolyte(LiCl) Flow Velocity 0.13 cm/s Catholyte (LiOH) Flow Velocity 0.33 cm/s

During operation of the electrochemical cell, samples were collected atthe catholyte inlet and outlet and anolyte outlet ports every 30minutes. Cell voltage was monitored at the cell terminals using ahandheld multimeter. The difference between the inlet and outletcatholyte hydroxide concentrations and the cell voltage were used tocalculate the efficiency and energy consumption of the cell.

Results

The results of the concentration of the catholyte are summarized inTable 2 and are shown in FIGS. 6 to 9. FIG. 6 demonstrates thedifficulty in maintaining a constant lithium hydroxide concentrationbased solely by adjusting the rate of water addition, in the absence ofreal-time measurements of the hydroxide concentration, because water canbe consumed or added to the catholyte by a variety of mechanisms,including electrolysis, evaporation, and migration across the membranewith lithium cations. In general, the data suggest that the higher theinitial concentration of lithium hydroxide, the more difficult the taskof maintaining the concentration constant through water addition.

The cell voltage was maintained at approximately 4.3-4.4 V for all ofthe experimental runs. FIG. 7 shows that cell voltage is relativelyindependent of hydroxide concentration, and implies that energyconsumption is largely driven by the electrical efficiency of theelectrode and membrane reactions. The cell gap in the FM01 electrolyzesused in this experiment (12-13 mm) is large compared to the cell gaptypically employed in commercial cells (2-3 mm), so a commercial cellwould be expected to have a lower cell voltage than those measured here.

FIG. 8 shows that current efficiency decreases with increasing lithiumhydroxide concentration. Without wishing to be bound by any one theory,it is believed this decrease in current efficiency may be due toincreased back-migration of hydroxide anions across the membrane fromthe catholyte to anolyte as the lithium hydroxide concentrationincreases. As shown in FIG. 9, this also results in increased energyconsumption, because all experiments were performed at the same currentdensity and the cell voltage was essentially constant. The experimentssuggest that a preferred concentration of lithium hydroxide in theelectrochemical cell may be between about 1-2 molar.

Table 2 summarizes the test results. As shown, lithium hydroxideproduction efficiency increases as lithium hydroxide concentrationdecreases, having an efficiency of up to about 80-88% for lithiumhydroxide solutions having a concentration of about 1 molar (2.4% byweight), Cell voltage is relatively independent of lithium hydroxideconcentration, so the efficiency also drives the energy requirement,which decreases to about 5 kWh/kg lithium hydroxide produced at aconcentration of about 1 molar. Lithium hydroxide production rate isgreatest with lower initial concentrations of lithium hydroxide.

TABLE 2 Summary of Results. LiOH LiOH Production conc. conc. Cell WaterEffi- Rate* Energy (Start) (Final) Voltage Added ciency kg LiOH/ kWh/kgTest M M V g/min % m²/hr LiOH 1 2.57 3.28 4.37 0.5 35 0.94 15 2 1.621.88 4.45 5 65 1.74 8 3 0.94 0.92 4.28 11 80 2.14 5 4 0.69 0.89 4.33 1088 2.36 5.3 *Calculated (Production rate = 2.68 kg LiOH/m²/hr ×efficiency).

Example 4 Carbonation

Chemical Reactor. Lithium hydroxide was carbonated using a 3 L Syrrisautomated batch reactor system (Syrris Ltd. 27 Jarman Way, UK), havingcontrols for sensing pH, temperature, reagent addition, and sampleextraction. The electrolytic studies detailed above suggest thatElectrolysis of lithium chloride could at most generate 1 molar or 2.4wt % lithium hydroxide solution. Indeed, this concentration has beenfound to be ideal for conducting carbonation studies without cloggingissues under our experimental conditions.

Carbonation Reaction Kinetics. The carbonation reaction kinetics oflithium hydroxide were determined by monitoring pH and metal ionconcentration in solution (using Atomic Absorption) as the reactionprogressed. Approximately 84 g of lithium hydroxide monohydrate wasdissolved in 2000 mL of water to prepare a solution having aconcentration of about 1 molar (about 2.4% by weight). The reactorjacket was heated using a 30:70 water-glycol mixture and the temperatureof the lithium hydroxide solution was maintained at about 95° C. Thesolution was stirred at 250 RPM with a mechanical stirrer constantlyduring the carbonation. The carbonating gas tube was maintained at adepth of at least 6 cm in the caustic solution to begin with and the gasflow rate was continuously monitored using a flow meter (MathesonTri-Gas, USA). As the carbonation progressed, the pH of the solutionincreased slightly and the completion of the reaction was determined bysudden drop in the pH of the solution, soon after the carbon dioxideflow to the reactor was stopped. The drop in pH coincides with theformation of lithium bicarbonate, which is unstable at highertemperatures. Therefore, the solution was heating/stirring of thesolution was continued to decompose lithium bicarbonate that had formedinto lithium carbonate. The decomposition of the lithium bicarbonateresults in increased pH which stabilized over time. Lithium ionconcentration was monitored during the reaction and showed that excesscarbonation of the solution can lead to bicarbonate formation.

During carbonation, a slight molar excess of carbon dioxide was added tothe lithium hydroxide solution to account for poor mixing of the carbondioxide into the lithium hydroxide solution. After completion of thecarbonation reaction, the solution was hot filtered because the lithiumcarbonate solubility in water decreases at increased temperatures. Thefiltered solids were first dried at about 60° C. for about 18 hours, andwere then dried at about 120° C. for about 24 hrs to ensure theconversion of any residual lithium bicarbonate that may present in thesolids back to lithium carbonate. The carbonation reaction was repeatedseveral times with a 1 molar lithium hydroxide solution under slightlydifferent experimental conditions, and both with and without lithiumcarbonate seeds. The results are shown in Table 3. Seeding of lithiumhydroxide solution with lithium carbonate crystals improved yields. Athigher carbon dioxide flow rates (e.g., at 3 L/min and greater), theyield of the carbonation reaction remained high. As shown in Table 3,carbon dioxide feed was maintained at about 2 L/min, although the totalamount of carbon dioxide added varied between about 1.25 and 2.5 moles(i.e., between about 0.625 and 1.25 molar equivalents). Experiment 1 inTable 3 included the addition of nitrogen gas to the carbonation vessel.Experiments 3-5 in Table 3 included the addition of between about 0.6%and 1.2% by weight lithium hydroxide seeds. The results show thatincreased reaction rate can allow for a reduction in the reactor size,and reduced overall cost associated therewith.

TABLE 3 Carbonation Reaction of a 2.4% by Weight Solution of LiOH^(†)Overall Lithium Carbonate Carbonation Solids Recovered Exp. ReactionConditions Yield (%)^(#) (%) 1 CO₂ (2 LPM, 2.5 moles) + 100.0% 57%* N₂(3.7 LPM) 2 CO₂ (2 LPM, 1.9 moles)   93% 73%  3 CO₂ (2 LPM, 1.5 moles) +  99% 82%  1.2% Li₂CO₃ seeds 4 CO₂ (2 LPM, 1.25 moles) +   93% 78%  0.6%Li₂CO₃ seeds 5 CO₂ (3 LPM, 1.3 moles) +   96% 82%  1.2% Li₂CO₃ seeds^(†)Prepared by mixing 84 g lithium hydroxide (LiOH•H²0) in 2 L water.^(#)Overall yield includes the amount of lithium carbonate/bicarbonatedissolved in solution and deposited inside the reactor walls.*excessively carbonated and filtered without converting LiHCO₃ back intoLi₂CO₃.

The methods described herein are suitable for the recovery of lithiumfrom brines or solutions having low or high lithium concentrations, inaddition to brines or solutions that include significant concentrationsof other ions, including multivalent ions.

As is understood in the art, not all equipment or apparatuses are shownin the figures. For example, one of skill in the art would recognizethat various holding tanks and/or pumps may be employed in the presentmethod.

The singular forms “a”, “an” and “the” include plural referents, unlessthe context clearly dictates otherwise.

Optional or optionally means that the subsequently described event orcircumstances may or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value and/or to the other particular value, along withall combinations within said range.

Throughout this application, where patents or publications arereferenced, the disclosures of these references in their entireties areintended to be incorporated by reference into this application, in orderto more fully describe the state of the art to which the inventionpertains, except when these reference contradict the statements madeherein.

As used herein, recitation of the term about and approximately withrespect to a range of values should be interpreted to include both theupper and lower end of the recited range.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereupon without departing from the principle and scope of theinvention. Accordingly, the scope of the present invention should bedetermined by the following claims and their appropriate legalequivalents.

We claim:
 1. A method for preparing lithium carbonate from a lithiumchloride containing solution, the method comprising the steps of:supplying a lithium chloride containing solution to a silica removalstep to produce a silica-lean lithium chloride containing solution; saidsilica removal step operable to remove at least a portion of silicapresent in the lithium chloride containing stream; supplying saidsilica-lean lithium chloride containing solution to a lithium chloridecapture step, said lithium chloride capture step being operable tocapture said lithium chloride from the silica-lean lithium chloridecontaining stream; recovering lithium chloride from the lithium capturestep to produce a lithium chloride rich stream; supplying the lithiumchloride-rich stream to an electrochemical cell, wherein theelectrochemical cell is maintained at conditions sufficient to produce alithium hydroxide-rich solution; and contacting said lithiumhydroxide-rich solution with carbon dioxide to produce lithiumcarbonate.
 2. The method of claim 1, further comprising a purificationstep for decreasing the concentration of at least one of calcium,magnesium, manganese or zinc in the lithium chloride rich stream afterthe lithium chloride recovery step, the purification step comprising:contacting the lithium chloride rich stream with a base; adding acarbonate such that at least a portion of calcium, magnesium, manganeseor zinc present precipitates as a solid; separating the precipitate fromthe lithium chloride rich stream to produce a solid waste precipitateand a purified lithium chloride rich stream, said purified lithiumchloride rich stream having a lower concentration of at least one ofcalcium, magnesium, manganese or zinc; and optionally contacting thepurified lithium chloride rich stream with an ion selective media toreduce the concentration of at least one of the ions selected from thegroup consisting of borate, calcium, magnesium, manganese and zinc. 3.The method of claim 1, further comprising concentrating the lithiumchloride-rich stream prior to supplying the stream to theelectrochemical cell.
 4. The method of claim 1, wherein said lithiumchloride containing solution is a geothermal brine.
 5. The method ofclaim 1, wherein the cathode is selected from nickel, catalyzed nickelmesh, stainless steel and coated stainless steel.
 6. The method of claim1, wherein the electrochemical cell includes an anode, wherein is adimensionally stable anode selected from titanium mesh coated withruthenium oxide, titanium mesh coated with platinum and carbon.
 7. Themethod of claim 1, wherein said lithium chloride capture step isolateslithium chloride and allows other anions and cations present in thesilica-lean lithium chloride containing solution to pass.
 8. The methodof claim 1, wherein the lithium containing solution is a smackoverbrine.
 9. A method for the preparation of lithium carbonate from alithium chloride containing brine solution, the method comprising thesteps of: providing a lithium chloride containing brine solution;removing at least a portion of silica present in said lithium chloridecontaining solution to produce a silica-lean lithium chloride containingsolution; isolating lithium chloride from said silica-lean lithiumchloride containing solution; recovering isolated lithium chloride toproduce a lithium chloride-rich solution; supplying said lithiumchloride-rich solution to an electrochemical cell and operating saidelectrochemical cell to produce a lithium hydroxide solution; recoveringthe lithium hydroxide solution from said electrochemical cell;contacting said lithium hydroxide solution with carbon dioxide toproduce a slurry that include lithium carbonate; and recovering lithiumcarbonate from said slurry.
 10. The method of claim 9, furthercomprising a purification step for decreasing the concentration of atleast one of calcium, magnesium, manganese or zinc in the lithiumchloride-rich solution after the lithium chloride recovery step, thepurification step comprising: contacting the lithium chloride-richsolution with a base; adding a carbonate such that at least a portion ofthe calcium, magnesium, manganese or zinc present precipitates as asolid; separating the precipitate from the lithium chloride rich streamto produce a solid waste precipitate and a purified lithium chloriderich stream, said purified lithium chloride rich stream having a lowerconcentration of at least one of calcium, magnesium, manganese or zinc;and optionally contacting the purified lithium chloride rich stream withan ion selective media to reduce the concentration of at least one ofthe ions selected from the group consisting of borate, calcium,magnesium, manganese and zinc.
 11. The method of claim 9, wherein thestep of recovering lithium carbonate from the slurry includes separatingthe slurry into solid lithium carbonate product and water.
 12. Themethod of claim 9, wherein said water has a pH of greater than 9, andfurther comprising the steps of adding an acid to produce an acidifiedwater having a pH of less than 7; and recycling the acidified water tothe step of recovering isolated lithium chloride.
 13. The method ofclaim 9, wherein the step of isolating lithium chloride comprisessupplying said silica-lean lithium chloride containing solution to alithium absorbent column.
 14. The method of claim 13, wherein thelithium adsorbent is a lithium aluminum intercalate.
 15. The method ofclaim 13, wherein the lithium adsorbent is a mixed metal oxidecomprising lithium and manganese.
 16. The method of claim 9, furthercomprising the step of increasing the concentration of lithium chlorideby removing at least a portion of the water in said lithiumchloride-rich solution prior to supplying the lithium chloride-richsolution to the electrochemical cell.
 17. A method for the preparationof lithium carbonate from a lithium chloride containing brine solution,the method comprising the steps of: supplying a substantiallysilica-free lithium chloride solution to a lithium chloride capturestep, said lithium chloride capture step being operable to capture saidlithium chloride from the silica-lean lithium chloride containingstream; recovering lithium chloride from the lithium capture step toproduce a concentrated lithium chloride rich stream; contacting theconcentrated lithium chloride-rich stream and a sodium carbonatesolution in a reaction vessel, wherein said sodium carbonate solution isprepared by contacting a sodium hydroxide solution with carbon dioxidegas, wherein the sodium hydroxide is prepared by electrolyzing sodiumchloride; separating a product stream from the reaction vessel toprovide a lithium carbonate product and a stream comprising sodiumchloride; and optionally recycling at least a portion of the sodiumchloride stream to the electrochemical cell for the production of sodiumhydroxide.
 18. The method of claim 17, further comprising a purificationstep for decreasing the concentration of at least one of calcium,magnesium, manganese or zinc in the lithium chloride-rich solution afterthe lithium chloride recovery step, the purification step comprising:contacting the concentrated lithium chloride rich stream with a base;adding a carbonate such that at least a portion of the calcium,magnesium, manganese or zinc present precipitates as a solid; andseparating the precipitate from a purified lithium chloride rich stream,said purified lithium chloride rich stream having a lower concentrationof at least one of calcium, magnesium, manganese or zinc.
 19. A methodfor the preparation of lithium carbonate from a lithium chloridecontaining brine solution, the method comprising the steps of: supplyinga substantially silica-free lithium chloride solution to a lithiumchloride capture step, said lithium chloride capture step comprisingcontacting the substantially silica-free lithium chloride solution witha lithium aluminum intercalate column operable to capture the lithiumchloride from the silica-lean lithium chloride containing stream;recovering lithium chloride from the lithium aluminum intercalate columnto produce a concentrated lithium chloride rich stream; contacting theconcentrated lithium chloride-rich stream and a sodium hydroxidesolution in a reaction vessel to produce a solution comprising lithiumhydroxide, wherein said sodium hydroxide solution is prepared byelectrolyzing sodium chloride in an electrochemical cell, saidelectrochemical cell comprising an anode, a cathode, and asemi-permeable membrane separating an anode chamber and a cathodechamber; contacting the solution comprising lithium hydroxide withcarbon dioxide gas in a reaction vessel to produce a solution thatincludes lithium carbonate; separating a product stream from thereaction vessel to provide a lithium carbonate product and a streamcomprising sodium chloride; and optionally recycling at least a portionof the sodium chloride stream to the electrochemical cell for theproduction of sodium hydroxide.
 20. The method of claim 19, furthercomprising a purification step for decreasing the concentration of atleast one of calcium, magnesium, manganese or zinc in the lithiumchloride-rich solution after the lithium chloride recovery step, thepurification step comprising: contacting the concentrated lithiumchloride rich stream with a base; adding a carbonate such that at leasta portion of the calcium, magnesium, manganese or zinc presentprecipitates as a solid; and separating the precipitate from a purifiedlithium chloride rich stream, said purified lithium chloride rich streamhaving a lower concentration of at least one of calcium, magnesium,manganese or zinc.